A basic framework of a physical layer in the LTE system is built based on the orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO). The OFDM is spread spectrum technology for adjusting data on multiple subcarriers in an OFDM symbol. The multiple subcarriers are spaced apart at accurate frequencies, so that the multiple subcarriers are orthogonal to each other. In the time domain, a guard interval such as a cyclic prefix (CP) may be added to each of the OFDM symbols, to prevent interference between the OFDM symbols. The cyclic prefix includes a normal cyclic prefix and an extended cyclic prefix. The MIMO, that is, multi-antenna technology, has important roles of improving a peak rate and reliability of data transmission, extending the coverage, suppressing interference, and increasing system capacity and system throughput. With continuous increase of requirements for the rate and spectrum efficiency, an important evolution aspect of the LTE system is to enhance and optimize the MIMO technology. Due to the limitation of an antenna framework of a traditional base station, the existing MIMO transmission scheme can generally control spatial distribution properties of a signal only in a horizontal plane, and cannot make full use of degree of freedom in a vertical dimension of the 3D channel, and cannot explore the potential of the MIMO technology for improving an overall efficiency and performance of a mobile communication system and the final user experience in a deep level.
The 3D MIMO technology can divide each vertical antenna element into multiple elements without changing the size of the existing antenna, in this way, another spatial dimension of the MIMO in the vertical direction is developed, and the MIMO technology is taken into a higher development stage. A wider improvement space of performance of the LTE transmission technology is opened up, so that it is possible to further reduce inter-cell interference, improve system throughput and spectrum efficiency.
However, the number of antenna ports for transmitting a reference signal supported in the 3D MIMO is increased, therefore, the existing reference signal patterns are no longer applicable, and it is required to develop a reference signal pattern applicable to more antenna ports in the 3D MIMO.